Piston and cylinder construction



w. M. ANDERSON 2,419,192

PISTON AND CYLINDER CONSTRUCTION Filed July 18, 1944 April 22, 1947.

6 Sheets-Sheet 1 FIG.2

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April 22, 1947- w. M. ANDERSON 2,419,192

PISTON AND CYLINDER CONSTRUCTION Filed July 18, 1944 6 Sheets-Sheet 2FIG? :llll'xl-lllllli, f Jun-I n WiLLlAM M. ANDERSON P 22, 1947- 'w. M.ANDERSON 92 I I PISTON AND CYLINDER CONSTRUCTIO Filod July 18, 1944 6Shoots-Sheet 3 FlG.ll m

- INVENTOR.'- WILLIAM M. ANDERSON ATTYS.

April 4 w. M. ANDERSON I PISTQN AND CYLINDER CQNSTRUCTIO" Filed July 18,1944 6 Sheets-Shut 4 INVENTOR WILLIAM M. ANDERSON.

BY urn.

W. M. ANDERSON PISTON AND CYLINDER CONSTRUCTION April 22, 1947.

Filed July 18, 1944 6 Sheets-Sheet 5 /NVEN7'0R.- WiLLlAM M. ANDERSONApril 1947. w. M. ANDERSON 2,419,192

PISTON AND CYLINDER CONSTRUCTION Filed July 18, 1944 s Sheets-Sheet e (D//VVENTOR.' WILLIAM M. ANDERSON v N 6 m N o Patented Apr. 22, 1947PISTON AND CONSTRUCTION William M. Anderson, Minneapolis, Minn.,assignor of one-fourth to'Oscar W. Giese, Washington, D. 0., andone-fourth to Maurice H. Graham, St. Louis Park, Minn.

Application July 18, 1944, Serial No. 545,462

24 Claims. (01. 309-1) This invention relates to reciprocating pistontype engines and is directed to improving the durability and wearinglife thereof. More particularly, the invention is directed to reducingfriction and wear resulting from sliding contact between cylinders andoperating pistons.

While the invention has utility for reciprocating piston engines ingeneral it is primarily concerned with internal combustion engineswhich, because of high operating temperatures and pressures therein,high wearing side thrust of the piston against the cylinder surface anddifllculty of maintaining efiicient lubrication between the surfaces ofthe cylinder and piston parts, present material and constructionproblems in obtaining long time wear-resistance which, for the mostpart, are more serious than experienced in other reciprocating engines,such as liquid and gas pumps, steam engines,'etc.

Engine cylinders, and internal combustion engine cylinders inparticular, are ordinarily formed of cast iron or equivalent relativelyhard metal. In some cases the cylinder block has been made of softermetals such as aluminum and aluminum alloys which, because of theirlighter weight and better heat conducting properties, provide certainobvious advantages. However, because such softer metals have relativelypoor wear-resistance under normal conditions in an engine cylinder underthe continual sliding contact of the piston and piston ring surfacestherewith, it has heretofore been found necessary when constructing thecylinder block of softer metals to insert a tubular sleeve of hardermetal such as steel as the cylinder wall to obtain satisfactory wearingqualities. Such practice decreases thermal efllciency and otheradvantages of the lighter metals, and involves various mechanicalproblems in construction, with the result that ordinarily it has beenmore usual to construct the entire cylinder block as well as the pistonand contacting cylinder walls of hard metals which have reasonably goodwear-resisting properties.

Internal combustion engine pistons are usually constructed of iron,although they may be, and sometimes are, constructed of aluminum. Compression seal is obtained with the cylinder wall by expansible ringscarried by the piston. Such rings are usually of hard metal and tend towear the cylinder walls, and this wear is supplemented by additionalwear caused by contact of other surfaces of the piston with thecylinder. Of course lubrication of the cylinder walls is provided in allengines to minimize wear, but nevertheless wear is a serious factor.

The problem of wear in reciprocating piston engines is a serious oneeven when the cylinder bore is composed of hard metals because costlyreboring of the cylinder and replacement of at least the piston ringsare necessary to overcome its effects after an extended running period.The

more rapid wear when cylinder bores are composed of softer metalsresults in such a short" running life for such cylinders as to maketheir use uneconomical and impractical despite inher ent advantages forcylinder bore purposes possessed by various of the softer metallicmaterials over the commonly used harder metals.

It is a general object of the invention to improve th wear-resistance ofengines whatever the composition of their cylinder bore.

It is a further particular object of the invention to so increase thewearing life of cylinders of softer metals such-as aluminum as to maketheir use practical and economically sound.

To carry out these objects the invention provides improvements both inthe piston assembly and cylinderconstruction. I prefer to employ a novelpiston assembly and novel cylinder construction jointly in order tosecure best results, but one of such features may be employed withoutthe other with lesser but at least fair results in improved wearinglife. The improved piston assembly and cylinder construction can be usedto advantage individually in' cylinders of both hard and softer metalsto improve wearing properties and minimize lubrication problems. Thecylinder construction is of greatest utility for cylinders of softermetals, but may also be employed to increase the wearing life ofcylinders of hard metals.

Among the individual features of the invention are the use ofnon-metallic sealing rings, the use of non-metallic pistons ofcompositions, such as carbon graphite, having lubricant retaining and/orself-lubricating properties, or alternately, the use of metallic pistonsequipped with special non-metallic fixed and/or expansible inserts orrings additional to scaling rings with lubricant retaining and/orself-lubricating properties, and the construction of the cylinders toinclude a series of small inserts formed and arranged to increasewear-resistance of the cylinder metal.

For internal combustion ngines such rings must not only be durable butheat resistant and, to minimize Wear of both cylinder and rings, therings should preferably have lubricant retaining properties. I prefer toemploy novel hard, non-metallic rings such as disclosed in my copendingapplication, Serial No. 534,300, filed May 5, 1944, and hereafter to bedescribed.

While the individual features of the piston assembly and the cylinderconstruction, may be employed independently, best results are securedwith all of them jointly. For example, employing an aluminum pistonequipped with non-metallic rings in an internal combustion enginealuminum bore cylinder, it was found that the engine stilloperatedsatisfactorily without noticeable loss in compression, and thecylinder and the ring showed only a slight degree of wear after somehundreds of hours. By incorporating a series of of the cylinder.

small wear-resistant inserts in an aluminum cylinder bore it was foundthe wear-resistance of the cylinder was greatly increased. By utilizinga non-metallic piston composed of carbon graphite having lubricatingproperties, a protective film was formed thereby on the cylinder wallwhich enhanced both the wearing properties of the cylinder and therings. The latter result was also obtained by employing metal pistonshaving fixed inserts and/or expansible ring-like carbon graphiteinserts.

,The novel cylinder insert construction here proposed comprises a seriesof relatively wearresisting narrow rings uniformly and narrowly spacedfrom each other lengthwise of the cylinder and preferably presentingcollectively a total area'no greater than half the surface areaPreferably also, such rings are inclined relative to the cylinder axis,and by adjustment of the angle of inclination of the inserts in relationto the diameter of the cylinder the proportionate contact of surfaceparts of the piston assembly made simultaneously with the respectivecylinder and insert surfaces under reciprocation f the piston may bemaintained constant and equal, all as hereafter more fully explained.

In the drawings: Fig. 1 is a side view of one embodiment of a pistonassembly according to the invention;

Fig. 2 is a fragmentary vertical section of the piston assembly of Fig.1 in an engine cylinder; Fig. 3 is a side elevation of a second pistonassembly according to the invention;

Fig. 4 is a fragmentary vertical section of the piston assembly of Fig.3 in an engine cylinder; Fig. 5 is a horizontal vertical section takenon the line 5-5 of Fig. 3;

Fig. 6 is a side elevation of a third form of piston assembly accordingto the invention;

Fig. is. a fragmentary vertical section of the piston assembly of Fig. 6in an engine cylinder;

Fig. 8 is a side elevation of a fourth piston assembly according to theinvention;

Fig. 9 is a fragmentary vertical section of the piston assembly of Fig.8 in an engine cylinder, and taken on line 9-+9 of Fig. 8;

Fig. 10 is a horizontal section taken on theline iD-IO of Fig. 9;

Fig. 11 is a side elevation of the piston assembly employed in theengine cylinder of Fig. 12; Fig. 12 is a fragmentary vertical section ofa preferred form of cylinder construction incorporating inclinedring-like inserts, and showing one preferred form of piston assemblytherein;

Fig. 13 is a side elevation of a piston assembly employed in the enginecylinder of Fig. 14;

Fig. 14 is a fragmentary vertical section of an engine cylinderincorporating ring-like inserts arranged at a different inclination thanin Fig. 12, and further showing a piston assembly there- Fig. 15 is anexplanatory view of a full-length engine cylinder with ring-like insertsin vertical section with a piston in side elevation therein, anddiagrammatically illustrating rotation of the crank shaft, the cylinderand piston being in accordance with Figs. 13 and 14;

Fig. 16 is a perspective view looking down on an air-cooled enginecylinder incorporating ringlike inserts in accordance with theinvention;

Fig. 1'7 is a vertical section of the cylinder of Fig. 17; a

Fig. 18 is a fragmentary perspective view of 4 I an assembly ofring-like inserts employed in the cylinder of Figs. 17 and 18;

Fig. 19 is an explanatory chart diagrammatically illustrating the areaof contact made by piston rings with ring-like cylinder' inserts andintervening land portions of the cylinder in five positions a, b, c, dand e of downward travel of a piston, with four different angles ofinclination of the insert rings relative to the cylinder axisrepresented in columns I, II, III and Fig. 20 is an explanatory chartalong the gen- 1 eral lines of Fig. 20, and illustratin the effect ofemploying piston rings narrower than the cylinder ring-like inserts;

Fig. 21 is a further explanatory chart wherein I the piston ring iswider than the cylinder ringlike inserts; and,

Fig. 22 is a diagrammatic view illustrating the relationship betweencylinder diameter and cylinder insert angle;

In Figs. 1 and 2 the piston assembly throughout its operative surfacescomprises hard, nonmetallic materials adapted to withstand thetemperature and pressure conditions encountered in internal combustionengines. Such materials are also adapted to produce a minimum offriction in sliding contact with engine cylinder walls in the presenceof a lubricant so as to minimize wear of the cylinder wall underreciprocation of the piston, and be themselves sufiicientlywearresistant to be operative without replacement over prolonged periodsof engine operation.

Insuch embodiment the piston body 30 comprises hard, fine grain carbongraphite such as commercially available on the market in cylindricalstock form from which the piston may be lathed to shape. The piston maybe molded from powdered carbon graphite with a suitable heatresistantbinder, such as water glass, under high pressure from thirty to fiftytons per square inch, or more, and baked at high temperature. The carbongraphite employed should have relatively good heat conductingproperties, since otherwise the top of the pistor-i'tends to spell underoperating conditions in an internal combustion engine cylinder, andpreferably should have a thermo conductivity of 70120 B. t. u./hr./sq.ft./F. The material should have a transverse strength of better than1500 and a compressive strength of better than 4000. The grain sizeshould be as small as practicable so as to avoid abrasion of thecylinder walls. A hardness of 35 to 45, or better, is deemed desirableto insure prolonged wear-resistance. In order that the piston be of adiameter to rather closely fit the cylinder, it is desirable that thecoeflicient of expansion of the carbon graphite be no greater than thatof the cylinder, and it may be somewhat less. A commercial carbongraphite which has proved satisfactory is Stackpole, grade 1101.

As will be seen in Fig. 2, the carbon graphite piston body 30 isprovided with a series of circumferential grooves 31 accommodatingsealing rings 32 backed by iron or other metallic expander rings 33. Asconventionally twoof the rings are located at the upper portion of thepiston. A third ring is located in the lower por-' tion of the piston;although the latter may be dispensed with.

Rings 32 are of a split, expansible type and are comprised of hard,non-metallic material. Preferably such rings are composed of hard moldedheat-resistant material such as woven or biaidedasbe'stos ropeor'tubing, treated with a heat-resistant hardening agent 'such'as waterglass and a fire-retardant agent such as Du Pont's CM," molded under apressure of between 40 tons and 50'tons per square inch, depending onthe width-of the ring and baked at a' temperature of. about 300 F., fora'period of about six hours, the ring and method of making the samebeing in accordance with my copending application, Serial No. 534,300,filed May 5,1944.

The operating surfaces of both the piston 30 and the non-metallic rings32, while diflering in their composition, and despite their hardness,are readily wetted by engine lubricant, and in fact are lubricantabsorbing, so as to create only a low amount of friction with theoperating surface of engine cylinder 31. Hence, despite theirnonmetallic character piston 30 and rings 32 are long-wearing underoperating conditions and prolong the life of the cylinder'surfaceagainst wear. I

Cylinder 31 may, as conventionally, be of cast iron, a relatively hardmetal. Despite its relatively good. wear-resistant properties a castiron' cylinder eventually wears, particularly in the intermediateportion thereof due to the side thrust of the piston against thecylinder wall when the engine crank and connecting arm are substantiallyinclined to the axis of the cylinder bore. Under such conditionsconventional metallic rings employed with conventional metallic pistonsdue to friction, and despite lubrication, eventually wear the cylinderto an oval cross-section. By employing the described piston and rings.the life of the cylinder against such wear is materially prolonged.

It is also contemplated to use a non-metallic piston assembly in anengine with cylinder 31 composed of light-weight metal such as aluminumand aluminum alloys with substantial increase in the wearing life of thecylinder as com-' pared with the employment in such a cylinder of anall-metal piston assembly. While the wearresistance of aluminum and likesofter metals is substantially less than that of cast iron, and in thepast has .not been found feasible for the cylinder bore, the employmentof the present pis-' ton assembly so increases the wearing life of sucha cylinder as to make it practical, particularly for smaller types ofinternal combustion engines.

The employment of carbon graphite for cylinder body 30 is preferableover other non-metalinwardly projecting portions ring, although notnecessarily so, is composed of carbon graphite, and serves the samefilm-forming function with reference to the cylinder wall as the piston30 of similar composition in the previous embodiment. Ring 45 is hereshown as a four-section split ring adapted to be expanded by a springmetal backing ringAli. Such ring tends to form a protective graphitefilm on the bore of cylinder 41 to protect the same against wear bysealing ring 42 and the metallic working surface of piston 40.

In the further embodiment of Figs. 6 and 7 the piston body is againcomposed of conventional metal composition, and sealing rings 52 arenon-metallic and of the composition previously described. In the skirtportion of the piston body is an annular groove 54 filled with a carbongraphite ring. or insert 55 which functions for the same purpose as theexpanslble carbon graphite ring 45 in the embodiment of Figs. 3 to 5with respect to the bore of cylinder 51. As shown, insert 55 issubstantially wider than seal- 8 rings 52. although this is notconsidered critical. I

In the embodiment of Fig. 8 a metallic piston body is provided withexpansible non-metallic split sealing rings 62 as in previousembodiments. In this case therings are located below the pivotal wristpin connection of the piston with the usual connecting rod. To avoid'loss of compression, the outer ends of the piston bore 63 for the wristpin are closed by plugs 64, preferably of carbon graphite. A fixedcarbon graphite insert 65 may be locatedin the skirt portion of thepiston below the rings. In addition to, or in lieu of, insert 65, thereis a lubricant absorbing fixed insert ring 69 surrounding the uD- perportion of the piston and seating in groove 68 formed therein. Groove 68at a plurality of circumferential points is provided with inwardextensions 68' opening interiorly of the hollow piston body. and suchextensions are filled with 69 of insert ring 69. The purpose of sucharrangement is to permit lubricant from the engine crank case acto beabsorbed therefrom by ring 69., Ring 59 lic material because carbongraphite itself not only absorbs lubricant, but itself has lubricatingproperties. In the course 'of engine operation graphite is depositedinthe form of a thin film on the cylinder surface which presents a highlypolished appearance, and such'fllmserves to increase the wear resistanceof the cylinder bore and minimize wear of the non-metallic piston andrings as well as of'the cylinder. A cylinde;- having a bore of aluminumappears to take the protective graphite film' more readily than iron,probably due to the wetting properties of aluminum, and better resultsare obtained with a piston assembly including graphite operatingsurfaces than where the piston assembly is composed entirely of othermaterials.

is thus rendered lubricating at its working urface to minimize frictionwith the surface of cylinder lil. Ring 69 is preferably a hard ring, andof carbon graphite composition to increase its cylinder lubricatingaction.

Whereas the piston assemblies heretofore described may be employed incylinders whose bore is constituted throughout of the same metal as themain cylinder casting, improved wearing qualities may be obtained byemploying cylinder inserts in the bore of different composition than thecylinder. The advantages are particularly great wherein the cylinder isformed of aluminum, its alloys or other light-weight relatively softmetals. In some instances the inserts may be composed of carbongraphite, but ordinarily I The entire piston assembly" need not benonmetallic, as illustrated in the embodiment of Figs. 3 to 5. Thereinthe piston body 40 may be made of cast iron, aluminum,;or other metallicmaterials. Sealing rings 42, here two in number, are again non-metallic,and preferably of the same composition as rings 32 intthe embodiment ofFig. 1. An additional ring 45, here the top metal of the cylinder.Because of the difference in coeflicients of expansion ofdifferentmaterials, it is important that the inserts be of such form asto minimize the difference in expansion as between the inserts andcylinder, and yet increase the wean-resistant properties of the cylinderbore throughout its circumference, and throughout at least thelongitudinal portions of the bore most subject to wear. It is importantin this connection that under high temperature conditions such asprevail in internal combustion engines that the inserts shall not becomeloose from in the cylinder bore are largely lost. That is to say, theuse of inserts of substantial length in I their greatest dimensions, forexample, a perforate or imperforate tubular sleeve or other insertextending uninterruptedly for the length of the cylinder, or asubstantial portion thereof, is undesirable. For thermal efliciency theinserts should be separated by continuous and frequent circumferentialland portions of the cylinder, and desirably both the inserts andintervening land portions should be continuous and unbrokencircumferentiallyto provide. uniform contact circumferentlally with theoperating surfaces of the piston assembly. That is to say, recurrentsmall inserts separated circumferentially by'intervening cylinder landportions are not desirable as likely to cause non-uniform wear atdifferent circumferentlal areas of the piston assembly, and as likely tofail to give proper wear-resistance to the cylinder'bore.

With the above qualifications in mind the present invention contemplatesthe use of wear-resisting inserts in cylinders in the form of axiallyand uniformly spaced relatively narrow rings in the cylinder, andseparated by intervening land portions of the cylinder of the same orderof width as the insert rings. In order to minimize wear, and to insurecontact of one circumferential portion of the piston assembly withinsert surface portions while another circumferential portion of thepiston assembly is in contact with the cylinder surface, the cylinderinsert rings are inclined rel- ,ativelto'the cylinder axis and to thepiston rings.

Through proper selection of the angle of inclination of the insert ringsin relation to the cylinder diameter and the width of the piston ringsit is possible tozsecure a constant ratio of contact of the pistonassembly with the cylinder insert and cylinder land surfaces as thepiston reciprocates in the cylinder. 7

The cylinder construction embodying inserts as just generally describedand preferred forms of piston assemblies adapted to increase the wearingqualities obtainable with the inserts alone will be understood fromFigs. 11 to 1'7.

In Figs. 16 and 17 I have shown a cylinder 1 cmbodying a series ofwear-resisting insert rings 8 arranged in uniform spaced relationlengthwise of the cylinder bore. The cylinder shown is an aircooledcylinder, but the invention is equally well adapted for liquid cooledcylinders. Ring inserts 8 are firmly anchored in the cylinder bore bycasting the cylinder around them.

The cylinder may be composed of cast iron, but the invention is ofgreatest importance when the cylinder is composed of softer, lesswear-resisting metals, usually of lighter weight, such as aluminum andaluminum alloys. The inserts will preferably be of a harder metal thanthe cylinder. In the case of aluminum cylindersI prefer to employ insertrings of cast iron, whereas in a cast iron cylinder I may employ insertsof chromium steel. In some cases a hard non-metallic insert of alubricant absorbing or lubricating composition, such as carbon graphite,may be employed, al-

though rings of such composition are better suited to engines other thaninternal combustion engines, since .in the latter engines the expansionof the cylinder under high operating temperatures may cause cracking ofthe inserts.

As best shown in Fig. 19 the inserts 8 are in the form of complete ringsor annuli so asto provide uniform protection throughout the entirecircumference of the cylinder bore. The rings may be entirely separatefrom each other, but for convenience they may be formed as an integralassembly of rings to facilitate the cylinder casting operation andinsure uniform spacing between the inserts. As shown in Fig. 19 smallspacing and connecting elements 8 are provided between adjacent insertrings. One such element only is preferably used between two rings, andalternate elements are circumferentially spaced from each other, so thatthe assembly can accommodate itself to longitudinal expansion of thecylinder without loosening or breaking the rings. While desirably insertrings 8 should have a coefficient of expansion as close to that of thecylinder metal as possible, it is found that in view of the relativelysmall dimensions of the inserts, and their arra ement, that differenceinthe coefllcients of expansion, for example, between cast iron andaluminum, does not cause difllculty.

After the cylinder is cast the bore is machined and finished in theusual manner to provide a continuous smooth working surface made up ofsurfaces of the insert rings and intervening land portions I of thecylinder. .-The width of the inserts and cylinder land surfaces ispreferably equal in order to obtain the full benefits in increased wearfrom employment of the-rings, and provide sufficient surface area of thecylinder metal at the working surface without unduly cutting down thethermo conductivity and other benefits arising from the presence of thecylinder metal at the working bore surface-of the cylinder. The width ofinsert rings 8 and cylinder land portion 1' is relatively narrow, and ofthe same order of dimension as the width of piston rings being employedin the cylinder. The main aim is to insure against the piston'ringstraversing a substantial area of the surface bore in contact only withcylinder land portions. I prefer to make the width of the insert ringsand cylinder land portions either the same as, or slightly less, thanthe width of the piston rings, but in some cases, particularly where itis desired to employ extremely narrow insert rings, the inserts and landportions may be wider. I

It is an important feature of the invention that the insert rings 8 beinclined to'the axis of the cylinder bore so that the piston rings,regardless of their width, shall at all times have bearing contact withone or more of the cylinderv inserts and never make bearing contactsolely with cylinder land portions. The angle of inclination will varywith cylinders of different bore diameter, and will depend on the widthof the inserts and cylinder land portions in relation to the width ofpiston ring employed, where the benefits of the insert construction areto be realized as fully as possible. It is preferred that the angleshould not exceed the minimum necessary to obtain the desired ratio ofsimultaneous contact of the piston rings and other portions of thepiston assembly with the respective surfaces of the cylinder inserts andcylinder land portions. It will be apparent that the greater the angleof inclination of insert rings 8 the greater will be their diameter inrelation to the diameter of the cylinder, and the total length of theinserts circumferentially should beas small as consistent with theobjects to be obtained in order to insure against injury to or looseningof the inserts under circumferential and longitudinal expansion of thecylinder with temperature conditions- Depending on the variables abovereferred to, the cylinder insert inclination will ordinarily be lessthan 15 for cylinder diameters not less than two inches, and-ordinarilywill range between'abollt and 11". In any event the angle may .bedetermined from the formula where D represents the cylinder diameter,where represents the width (axially) or the insert ring'and/or the widthof the cylinder land portions between rings, and :2 represents thefraction or multiple of W. The edges of the low side ofthe insert are tobe below the diametrically opposed edge portions at the high side oftheinsert. If the width of the insert and the width of the land portionare equal to each other, and equal to the width of the piston ring, orequal to twice the width of the piston ring, the value of a: will be 2,whereas if the width of the insert and cylinder land are equal to eachother, but double the width of the piston ring a: can be as low as "/2.The effect of varying the value of :cW will become apparent later.

In the embodiment of Fig. 12 is shown a cyline der 11 such as has beendescribed havin insert rings 18' spaced by intervening land portions 11'of the cylinder, the widths being the same. Working in such cylinder isa piston having sealing rings 12, and more clearly illustrated in Fig.11. Assuming that cylinder 11 is formed of a soft metal such as aluminumthe cylinder inserts 18 may be composed of carbon graphite, butpreferably will be cast iron. Piston body 10 is nonmetallic and composedof carbon graphite, and

sealing rings 12 are preferably non-metallic also,

and preferably of the composition previously described. The cylindersass bore diameter of 2% inches, and the low sideisif the insert ringsau ios that they may be wider or narrower. If the piston rings-are onlyone-half the width of the in serts it is preferable to use a steeperangle of inclination for the inserts as in Fig. 14. Again, if narrowinsert rings are employed the angle of inclination may be the same, butcan be reduced to the angle of inclination in the embodi ment of Fig.12. The significance of the angle of inclination of the inserts will beunderstood by reference to Fig. 19. The number of insert rings to beemployed is subject to variation. In Fig. 15 the rings are shown asextending uniformly throughout substantially the entire length of thecylinder. However, the inserts maybe confined to the portion of thecylinder subjected to greatest wear under reciprocation of the piston,that is, the area traversed when the connecting rod and crank shaft ofthe engine are at their greatest angles to the axis of the cylinder,which will roughly be between and 120 on the power stroke and between240 and 300 on the returmstroke. As further shown in Fig. 15 theinclination of the cylinder inserts is in a direction at right angles tothe engine crank shaft. Since the side thrust of the piston is to theleft on the power stroke, and to the right on return stroke according tothe showing in Fig. 15, the inclination is towards the directionpfmovement of the piston. The high side of the insert rings is on theleft, and the low side on the right on the downward power stroke of thepiston. 0n the downward or power stroke the piston rings will firstcontact the left side of the insert rings, whereas on the upward orretumstroke the piston rings will first contact the right side of the insertrings.

The-significance oi the angle of inclination of the inserts previouslyreferred to will be understood from Fig. 19. At the top of thefour-col-' umns are illustrated diagrammatically a single piston sealingring PR in broken lines in relation to three cylinder insert rings,CR-l, CR! and is intended to be half the width of the insert below thehigh side of the insert. ln the above formula for the angle ofinclination reg-pals -With a cylinder formed with inserts a'nietallicpiston may be employed as illustrated in Figs l3 'and 14. Therein thecylinder body 81 is formed 'with insert rings 88 separated by cylinderland *qportions 81'. Piston is a' metallic piston, for example,aluminum, provided with sealin -rings 82. In some cases rings 82 mayalso be resilient metallic rings, but betterwearing qualities e obtainedby employing non-metallic compositi 1 rings such as before described. Anadditionai -i non-metallic ring 85 is provided on the piston, preferablycomprising carbon graphite and adapted to form a protective film on thecylinder bore.

As shown such insert is a rigid insert located in the skirt of thepiston, as in the embodiment of Fig. 6, but it will,be understood suchinsert may be located elsewhere on the piston body and/or be ofexpansible type as, for example, in the piston assemblies of Figs. 3 and8. The angle of inclination of insert rings 88 is greater than that inFig. 12. The low side of the inserts are twice the width of the insertsbelow the diametrically high. side of the inserts. In the formula abovegiven a: equals 2. As in Fig. 12-the piston rings .2 are of the samewidth as the inserts 88 and cylinder land portions 81', but it isunderstood 1,; with the (JR-3. The two spaces CL between the insertrings represent intervening land portions of the cylinder. The insertsare shown at four different angles of inclination in the respectivecolumns. In column I th low side of the inserts are onehalf their widthbelow their high sides, and in columns II, III and IV, respectively, thelow sides of the inserts are 1, 1 and 2, times their width below thhigh-side. The .five views in each 001! umn diagrammatically representthe amount of contact made by th piston ring- PRwith one or more of theinsert rings and one or more of the cylinder land portions undermovement of the piston in the cylinder. designated a, b, c, d and e, andthe positionof the piston ring relative to the insert rings and landportions is shown by the key to the left of colr b umn I.-+.'fn thecolumns the individual views are hatcfred to represent portions ofone-half the ring ,.-e's5wiewed from the side which contact. cylinderinsert surface and are unhatched in the piston ring surface portionwhich contacts cylinder land surface.

i e insert angle as in column I the amount t of the piston ring madesimultaneously insert and land surface varie s considerably as thepiston ring moves axially. In posi- Egtions a and b, also in e whichcorresponds to a, v

the piston ring has three-quartersof its working rface in contact withinsert surface, and only one-quarter in contact with cylinder landsurface, whereas in positions 0 and d only one-quarter of the pistonring surface is in contact with The five positions are insert surfacewhile three-quarters is in contact with land surface. When the angle ofinclination is increased so that the low side of the inserts.

are the full width of the insert below the high side as in column II,the piston ring makes the same amount of contact with insert surface andcylinder land surface in positions a, c and e, but makes three-quarterscontact with the insert in position b, and three-quarters contact withcylinder land surface in position d. In column III where the angle isfurther'increased so that the low sides of the inserts are on andone-half times their width below their high sides the fluctuations incontact are less, but the piston ring still has a greater amount ofcontact with the insert surface in some positions and with the. cylinderland surface in other positions. In positions a, d and 8 more thanone-half thecontact of the piston ring surface is with cylinder landsurface, while in positions b and c more than one-half the contact ofthe piston ring is with insert surface. In

column IV, where the angle is increased so that the low side of theinsert rings are twice the insert width below their high sides, aconstant 1:1 ratio of contact of the piston ring with the insert andcylinder land surfaces is obtained in all positions. That is to say,one-half of the working surface of the piston ring contacts insertsurface, and the remaining half contacts cylinder land surface. Such anoperative condition is now considered as ideal for best results, butwithin the scope of the invention the angle may be made smaller orgreater. As will be understood from columns I, 11 and III the ratio ofcontact changes when the angle is decreased. When the angle is increasedstill further from that shown in column IV a constant ratio of contactis still obtained, but as previously pointed out it is desirable tomaintain the angle at a minimum so that the circumferential length ofthe rings is as short as possible for a cylinder of any given diameter.

In Fl'g. 19 in all instances the insert rings and cylinder land surfaceshave been taken as the same width as the piston rings. Such condition isnot necessary. For example, the piston ring may be one-half the width ofthe inserts. With the same angle of inclination of the inserts as incolumn IV of Fig. 19 the piston ring always I will have one-half of itssurface in contact with insert surface and one-half in contact cylinderland surface. This is represented in Fig. 21. Again, the inserts andcylinder land portions may be narrower than the width of the pistonrings. Where this is true a lesser angle of inclination may be employedfor the inserts. sents a situation where the cylinder inserts and landportions are one-half the width of the piston rings. A 1:1 ratio ofcontact of the piston ring with insert surface and with land surface isalways obtained where the low side of the inserts are one insert width(or one-half piston ring width) below the high insert sides.

Fig. 21 repre- It will be of course understood that the angle A to Dunder the conditions shown in column I will'range from about 258 forangle A down to about 1.78for angle cylinder inserts and cylinder landportions have a width of 1; inch., The corresponding angle values forcolumn II would range from about 5.36" down to 3.58, and for columns 111and IV respectively the values would range from about 8.05 to 536, andfrom about 10.'72 to about 6.12". It will be understood that these aremerely suggested values, and the angles for any cylinder size may be'varied, and to obtain the conditions illustrated in Figs. 19 to 21 willhave to be varied depending on the width of the cylinder inserts andland portions. Because the circumference of the inserts progressivelyin-. creases with'the angle of inclination differences; in thecoeflicients of expansion of-the inserts and cylinder may result in atendency of the inserts to loosen or otherwise change their relationshipwith the cylinder Wall if the angle of inclination is increased unduly.It is therefore considered desirable that the angle of inclination be nogreater than necessary to accomplish the objects above pointed out,thereby keeping the difference in circumference between the cylinder andthe inserts. It now appears to me that the angle of inclination shouldnot exceed 15 degrees.

It will be understood fromthe variou illustrative, but not limiting,embodiments of the invention which have been described that theinvention provides increased wearing life for engine cylinders ingeneral and internal combustion engine cylinders in particular,regardless of the composition of the cylinder bore although being mostimportant for cylinders of any appropriate light weight and/or thermallyefficient metals whose wear-resistance is objectionably low. The variousindividual features of the invention while best serving in combinationto cooperatively atgraphite.

2. A piston assembly including a piston body having a cylindricalworking surface of hard non-metallic composition, circumferentialgrooves in the piston. and expansible split sealing rings of hardnon-metallic composition supported in said grooves. v

3. A piston assembly including a metallic pistonv body having acylindrical working surface and being formed with a plurality ofcircumferential grooves, an expansi-ble. lubricant-requiring splitsealing ring of hard non-metallic composition seating in one. of saidgrooves, and said piston having a circumferential surface portion in theform of an' annular lubricating element of hard carbon graphite seatingin another of. said grooves.

4. A piston assembly including a metallicv piston body having acylindrical working surface and having formed with a plurality ofcircumferential grooves, an expansible lubricant-requiring sealing ringof hard non-metallic composition in one of said grooves, and said pistonhaving a circumferential surface portion in'the form of a hardexpansible lubricating ring in another of said grooves.

D, assuming that the 5. A piston including a hollow piston body, acircumferential groove in the outer surface of said body, an annularbody of hard lubricantabsorbing composition located in said groove, saidgroove having inward extensions communicating with the hollow interiorof the piston body so that lubricant within the piston interior may beabsorbed by said annular body.

6. An internal combustion engine piston assembly comprising a pistonbody having circumferential grooves, heat-resistant expansible sealingrings of lubricant-requiring non-metallic composition seating in atleast some of said grooves, and at least an annular zone of the pistoncomprising heat-resistant lubricating'material adapted to applylubricant to the wall of an engine cylinder.

7. An engine cylinder of relatively soft metal and insert means forincreasin the wearing lift of the cylinder comprising a series ofrelatively narrow insert rings of wear-resistin composition surroundingthe cylinder bore and ,being separated by relatively narrow interveningannular land portions of the cylinder metal.

8. An engine cylinder having a bore and a series of relatively narrowinsert rings of wearresistant composition surrounding said bore anduniformly separated from each other by relatively narrow annular landportions of the cylinder, said inserts being inclined to a transverseplane of the cylinder at an angle measured by not less than one half theaxial width of one of said land portions.

9. An engine cylinder having a bore and a series of relatively narrowinsert rings of wearresistant composition surrounding said bore anduniformly separated from each other by relatively narrow annular landportions of the cylinder, said inserts being inclined to a transverseplane of the cylinder at an angle measured by at least twice the axialwidth of one of said land portions.

10.,An engine cylinder according to claim 8 wherein the inserts andintervening land portions surrounding the cylinder bore are of the sameaxial width.

11. An engine cylinder comprising a metallic cylinder body having abore, and a series of axially spaced insert rings of harder metal thanthe cylinder body surrounding the 'bore and separated by annular landportions of the cylinder metal.

12. A cylinder according to claim 11 wherein the insert rings andcylinder land portions are relatively narrow and are inclined at arelatively small angle to a diameter of the bore.

13. An engine comprising a cylinder body and a piston assembly workingin the cylinder bore comprising a piston body formed with sealing ringgrooves and having at least an annular portion ofits cylindercontactingsurface composed of material adapted to apply lubricant to thecylinder bore, and hard lubricant-requiring nonmetallic expansiblesealing rings seating in the grooves of the piston body.

14. An engine comprising a cylinder body having a bore defined by ametallic interior wall and a piston assembly working in the cylinderbore comprising a piston body having a cylindrical working surface ofnon-metallic composition, circumferential grooves in the piston body,and hard non-metallic expansible split sealing rings seating in saidgrooves.

15. An' engine comprising a cylinder body of relatively soft metal, apiston assembly working in the cylinder bore comprising a piston bodyhaving at least an annular non-metallic surface portion composed ofmaterial adapted to lubricate the cylinder bore, circumferential groovesin the piston, and non-metallic sealing rings seating in said grooves.

16. An engine comprising a cylinder body of relatively soft metal, apiston body having a nonmetallic cylindrical surface and working in thecylinder bore, grooves in the piston body and hard non-metallicexpansible sealing rings seating in said grooves.

17. A reciprocating engine comprising a cylinder body and a pistonassembly working in the cylinder bore, said cylinder incorporating aseries of axially spaced narrow wear-resistant insert rings surroundingthe bore and separated by narrow annular land portions of the cylinderbody, and the piston assembly including a piston body havingcircumferential grooves, and hard nonmetallic sealing rings seating insaid grooves.

18. An engine according to claim 17 wherein the cylinder insert ringsare inclined to the sealing rings on the piston.

19. An engine according to claim 17 wherein the cylinder insert ringsand annular cylinder land portions are of the same Order of axial widthas the piston sealing rings, and the inserts are so inclined to thepiston ring that the piston rings simultaneously contact insert andcylinder land surface portions through traverse of the rings of the areaof the cylinder containing the insert rings.

20. An engine according to claim 17 wherein the cylinder insert ringsand annular cylinder land portions are inclined to the piston sealingrings, the width of the insert rings and land portions, and their angleof inclination, being such in relation to the piston sealing rings thatduring traverse of the piston the piston sealing rings will continuouslymake substantially equal contact with insert ring and cylinder landsurfaces.

21. An engine cylinder having an interior wall defining a bore and aplurality of insert rings of wear-resistant composition embedded in saidinterior wall and surrounding the bore, said insert rings being axiallyspaced from one another by intervening annular land portions of saidinterior wall of the cylinder.

22. An engine cylinder having an interior wall defining a bore and aplurality of insert rings of wear-resistant composition embedded in saidinterior wall and surrounding the bore, said insert rings beinguniformly inclined to the axis of the bore and being axially spaced fromone another by Number intervening annular land portions of said interiorwall of the cylinder.

23. An engine cylinder according to claim 22 wherein the insert ringsareinclined at an angle of less than 15 degrees to a diameter of thebore.

24. An engine cylinder having an interior wall defining a bore and aplurality of insert rings of wear-resistant composition embedded in saidinterior wall and surrounding the bore, said insert rings being ofcarbon graphite, and being axially spaced from one another byintervening annular land Portions of said interior wall of the cylinder.

-WILLIAM M. ANDERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 1,264,871 Jefferies Apr. 30, 19181,955,292 Heintz Apr. 17, 1934 1,010,787 Nilson Dec. 5, 1911

